Speech is a critical means of human communication. Likewise, numerous other species also employ vocal communication systems for exchanging information with conspeciflcs. Critical to every human and nonhuman animal vocal communication system Is the ability to distinguish conspeclfic vocal signals from other sounds in the environment. Despite its significance, our understanding of the neural mechanisms underlying this recognition process in cortex is limited. Building on work during the K99 portion of this grant, here we aim to test the test the perceptual and neural basis of vocal signal recognition during antiphonal calling, by parametrically manipulating the acoustic stmcture of a vocal signal. Antiphonal calling Is a natural, species-typical vocal behavior that Involves the reciprocal exchange of long distance vocalizations. Aim 1 will test the functional contribution of individual acoustic features for recognition of a species-typical vocalization during antiphonal calling at the perceptual level. Specifically, we vifill create synthetic replicas of naturally produced vocalizations and manipulate the acoustic structure to test how individual features contribute to vocal signal recognition. In Aim 2, we will record neural activity from freely-moving individuals engaged,in the same vocal behavior and examine the responses of neurons in the prefrontal and auditory cortex. In one set of experiments we will record the nomnal activity of neurons as subjects engage in antiphonal calling, while in a second set of experiments we will utilize the same procedure as In Aim 1 and manipulate the structure of the vocalizations during test sessions. These two types of experimental sessions will permit us to test both the baseline neural response to vocalizations during antiphonal calling, but whether neurons In either area show changes in reponses when aspects of the call structure are modified. Ultimately data such as these are needed in order to eluciate the neural processes underlying vocal signal recognition in cortex. Given the number of patients afflicted with speech recognition problems through either disease or injury, a more comprehensive understanding of how cortex accomplishes this task is necessary for addressing these Issues clinically.